From: Paul Chaignon <paul.chaignon@gmail.com>
Date: Tue, 9 Aug 2016 16:38:05 +0000 (+0200)
Subject: Motivate delete() before update() in tutorial (#651)
X-Git-Tag: v0.2.0~16
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=1e45e67aac20907f49f0105782ae4ed9fd4126a4;p=platform%2Fupstream%2Fbcc.git

Motivate delete() before update() in tutorial (#651)

This delete() is required because of a kernel bug:
https://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=a6ed3ea65d9868fdf9eff84e6fe4f666b8d14b02
---

diff --git a/docs/tutorial_bcc_python_developer.md b/docs/tutorial_bcc_python_developer.md
index e26dcff..9cd5718 100644
--- a/docs/tutorial_bcc_python_developer.md
+++ b/docs/tutorial_bcc_python_developer.md
@@ -162,7 +162,7 @@ Things to learn:
 1. ```BPF_HASH(last)```: Creates a BPF map object that is a hash (associative array), called "last". We didn't specify any further arguments, so it defaults to key and value types of u64.
 1. ```key = 0```: We'll only store one key/value pair in this hash, where the key is hardwired to zero.
 1. ```last.lookup(&key)```: Lookup the key in the hash, and return a pointer to its value if it exists, else NULL. We pass the key in as an address to a pointer.
-1. ```last.delete(&key)```: Delete the key from the hash.
+1. ```last.delete(&key)```: Delete the key from the hash. This is currently required because of [a kernel bug in `.update()`](https://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=a6ed3ea65d9868fdf9eff84e6fe4f666b8d14b02).
 1. ```last.update(&key)```: Set the key to equal the value in the 2nd argument. This records the timestamp.
 
 ### Lesson 5. sync_count.py